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Hey y’all, I have a 2009 Z51 and I just finished a cam install. The vehicle has 100,000 miles on it so I also did lifters and lots of other supporting mods. I was just finishing up and I was under the car putting the exhaust back on when a drop of coolant hit me in the forehead. I look up to see a leak coming from the seam on my head to the block.
after my fit of rage, I found that the head gaskets were on correctly and the leak had to be coming from the head gaskets.
I was sure to clean the bolt holes and clean the sealing surface with a carbide scraper during the install. While disassembling it today to try to find the problem, I look over and saw two new head bolts on my toolbox mixed in with the old ones.
my question is would a couple old head bolts being installed cause a leak before the engine is even turned over.
I also noticed the bolts were slightly different from the old ones. However, I’m probably going to end up ordering ARP head studs and some cosmic gaskets for a little more clamping force.
New and old head bolts are different Gasket leak gasket leak
Cometic gaskets (I assume that's what you meant) are known for being less forgiving than stock gaskets of imperfect surface finish.
thanks for the response, it is the same head going on the same block so I assumed there wouldn’t be any problems. I guess it’s silly for me to assume and yes, I did mean Cometic. Is there a better brand of gasket you would recommend?
If you re-used some of the old head bolts, that could be the problem. They are torque to yeild, 1 time use. Very possible that re-using them, they are not providing the proper clamping force.
ARP hardware is the way to go. Definitely the ARP head bolts. Even better if you go with the ARP studs. And I would highly recommend the ARP thread chaser as well.
The ARP studs are ideal really. They give more clamping force because they engage the full length of threads from the block. More importantly, they give a more consistent clamping force because when you are torquing them, the clamping forces are from the nut turning on the stud rather than the threads of the bolts turning in block threads. The block threads are not a uniform in surface roughness as the ARP threads.
As for what head gasket to use, the OEM GM head gaskets really are the best. Only time I would go with Cometic is if I was trying to change the compression ratio or amount of squish/quench.
And when I have removed heads on LS engine, the majority of my effort is spent cleaning the threads in the block. I make multiple passes with a thread chaser, cotton swabs, compressed air, and brake clean so that there is no residue of anything in the bolt holes and threads.
I'm personally doubtfull that a used bolt is the cause. Are you absolutely sure it's leaking, not just a drop that was leftover or spilt filling?
I’m sure it’s not leaking from somewhere else. I laid under the car for about 10 minutes and was able to watch it slowly come out of the seam. When I wiped it off, it would reappear in the same spot about 10 minutes later.
I was also doubtful that one or two bolts would cause it to leak like that. I’m thinking that it’s a combination of a couple used bolts and not cleaning out the threads good enough.
I use factory head bolts and Texas speed gaskets.
If you re-used some of the old head bolts, that could be the problem. They are torque to yeild, 1 time use. Very possible that re-using them, they are not providing the proper clamping force.
ARP hardware is the way to go. Definitely the ARP head bolts. Even better if you go with the ARP studs. And I would highly recommend the ARP thread chaser as well.
The ARP studs are ideal really. They give more clamping force because they engage the full length of threads from the block. More importantly, they give a more consistent clamping force because when you are torquing them, the clamping forces are from the nut turning on the stud rather than the threads of the bolts turning in block threads. The block threads are not a uniform in surface roughness as the ARP threads.
As for what head gasket to use, the OEM GM head gaskets really are the best. Only time I would go with Cometic is if I was trying to change the compression ratio or amount of squish/quench.
And when I have removed heads on LS engine, the majority of my effort is spent cleaning the threads in the block. I make multiple passes with a thread chaser, cotton swabs, compressed air, and brake clean so that there is no residue of anything in the bolt holes and threads.
Thanks for the reply!
I think I’m gonna order some ARP studs and oem gaskets as I was using Texas speed gaskets before with oem bolts. The thread chaser I used to clean out the bolt holes was a used bolt that I cut a slit in. So it’s totally possible that there was some residue left at the end.
I also used a carbide scraper to clean off the sealing surface to the point where I was able to see the factory machine marks. However, my garage is pretty dimly lit so I could’ve missed a spot.
Im going to suggest its either head or block prep.
Check the heads are level and square along with the block, lay a straight edge across them and check.
With no pressure on the cooling system that's a huge leak path then, as above check your surfaces for flat and make sure there's not something that got damaged somewhere. You could put 4 bolts holding the entire head down and no coolant should be dripping out like that if the surfaces and gasket are good.
Also when you redo this whether you have studs or bolts. Tighten the heads up like normal. If you use ARP stuff use their assembly lube. Let it sit overnight. Go back and put torque wrench on the final setting (say 70 foot pounds) and tug on each one and see if they move. I have found on mine that of the 20 big bolts, 3 went a little further (say 1/8+ turn) the next day.
The head bolts stretch when new and first torqued. Used bolts would result in a different torque, not saying that is your root cause but its very clear the fluid is coming from the head-to-block mating.
Head gasket leak
